The invention concerns disperse dyes for dyeing polyester-based fibers. In particular, the invention concerns disperse dye mixtures which have good fastness even on polyester-based fibers of fine denier which are disadvantageous in terms of light fastness, and with which mixed fibers where the thickness of the polyester-based fibers differs (mixed fibers of different fineness) or fiber mixtures comprising polyester-based fibers which can be dyed with cationic dyes and regular polyester-based fibers can be dyed the same color.
Cloths comprising polyester-based fibers are often used as the material for automobile seats, but more recently a demand has arisen for richer seat colors as more emphasis has been placed on the fashion aspect of the interior furnishing of automobiles. However, automobile seats are often exposed to high temperatures and sunlight when the cabin is closed and so color fading of the seats is liable to arise and it is difficult to ensure that the beautiful color will be retained over a prolonged period of time. Disperse dyes are generally used for dyeing polyester-based fibers, but dyes which have especially good light fastness must be used in the case of automobile seat applications. Moreover, more recently there have been many cases where fine denier polyester-based fibers have been used for automobile seat materials, and when these are dyed using the same dyes it is observed that the light fastness is worse than that observed when regular polyester-based fibers have been used. Against the background of these facts a demand has arisen at the present time for dyes for automobile seats which have better light fastness than that in the past.
In the past no dye which had good light fastness and with which dyeing could be carried out with good reproducibility with these fine denier polyester-based fibers in particular had been discovered. Then, the present inventors took up this problem and Japanese Patent Application 2002-338636 was made.
More recently, from the viewpoint of the diversity of taste and fashion, automobile interior furnishings comprising mixed fibers comprising polyester-based fibers of different thickness and automobile interior furnishings comprising polyester-based fibers which can be dyed with cationic dyes and regular polyester-based fibers have been produced.
Dyes of the three primary colors designed for automobile interior furnishings were known in the past (for example, see Japanese Unexamined Patent Application Laid Open H4-164969 and Japanese Unexamined Patent Application Laid Open H9-176509), but even when these dyes are used it is difficult at the present time to dye these automobile internal furnishings, and especially car seats, the same color with good reproducibility and with excellent light fastness.
U.S. Pat. No. 7,824,451 discloses the use of a dye mixture which comprises a blue colored dye mixture which contains from 10 to 60 wt % with respect to the total pigment fraction of a blue pigment which is a mixture of the two isomers which can be represented by structural formula [1]

wherein one of X1 and X2 represents NO2 and the other represents OH,
from 60 to 10 wt % with respect to the total pigment fraction of a blue pigment which can be represented by structural formula [2]

wherein R1 represents —C3H6OCH3, —C3H6OC2H5 or —C3H6OC2H4OCH3, from 10 to 30 wt % with respect to the total pigment fraction of the blue pigment which can be represented by structural formula [3]

and from 20 to 0 wt % with respect to the total pigment fraction of a blue pigment which can be represented by structural formula [4]

wherein R2 represents a hydrogen atom or a C1 or C2 alkyl group, and R3 represents a hydrogen atom, a C1 or C2 alkyl group or a C1 or C2 alkoxy C1 or C2 alkyl group.